The present invention relates to a container for a compressed fluid and in particular, although not exclusively, to a container for a compressed refrigerant such as carbon dioxide or nitrogen.
It is known to store compressed fluid and in particular gas in metallic vessels such as cylinders and tans. The volume of compressed gas stored within the vessel is governed by the well known equation Volume=Pressure/Temperature. Therefore, the volume of stored gas can be increased by either increasing gas pressure or decreasing gas temperature. In order to withstand high pressures the vessels have thick metallic walls. Further, the vessels are also often insulated to reduce the gas temperature and thereby maximise the storage volume. As a result the vessels are often very large and very heavy, and therefore particularly unsuited to applications were only small volumes of compressed gas may be required.
Also, these known vessels are typically in the form of closed or sealed cylinders. The cylinders define an internal space for holding the compressed gas. As a compressed gas is used, the gas pressure within the vessel decreases. Often, the most useful form of the compressed gas is when it is compressed to an extent that it is in the form of a liquid, for example liquid carbon dioxide or liquid nitrogen. The compressed gas can be held in a liquid form provided the pressure and temperature conditions within the vessel are maintained at predetermined levels. However, a problem with the current relatively large volume vessels is that gas pressure within the vessel decreases quickly as the liquid within the vessel is depleted. The decrease in pressure causes the boiling of the liquid which is a substantial drawback when the liquid is being used as a refrigerant.
The present invention was developed with a view to providing a relatively small volume container for holding a compressed gas in which one or more of the above described deficiencies may be reduced
According to the present invention there is provided a container for a compressed fluid, the container including:
length of tube formed into a coil and provided at one end with a first valve for controlling flow of the fluid out of the container, said coil being in the form of a helix having a first set of turns that are disposed about a vertical axis, and wherein said first valve is disposed at a height or level no greater than that of the lowest of the turns; and, heat insulating means enveloping said tube
Preferably the helix includes a second set of turns disposed within the first set of turns.
Preferably the container includes a pressure relief valve at an opposite end of the tube and wherein the opposite end is proximate a highest one of the turns,
Preferably the heat insulating means comprises a setable thermally insulating foam.
In an alternate embodiment, the heat insulating means comprises an evacuated sleeve coaxially formed with and about an outer surface of the tube.
Preferably the container includes one or more straps for binding the turns of the coil together.
Preferably, the container further includes an exterior thermally insulating housing which houses the tube and the heating insulating means.